The increasing integration of LSIs has led to finer and finer circuit line widths of semiconductor devices. An approach employed to form desired circuit patterns on semiconductor devices uses a step-and-repeat exposure system to reduce and transfer, onto a wafer, a high-precision master pattern (also called a mask, or a reticle particularly when used in a stepper or scanner) formed on a piece of quartz. The high-precision original pattern is written with an electron beam writing apparatus by use of a so-called electron beam lithography technique.
In an electron-beam drawing apparatus, various settings including focusing are performed on the basis of the resolution and the aperture angle of the beam. For example, the beam resolution is calculated on the basis of a predetermined expression from a beam intensity distribution obtained by scanning and applying an electron beam to a dot pattern (metal pattern) on a substrate, measuring reflected electrons, and calculating the beam intensity distribution from the measurement result (for example, see Japanese Unexamined Patent Application Publication No. 2007-188671 and Japanese Unexamined Patent Application Publication No. 2007-234263).
In order to improve the drawing accuracy of the electron-beam lithography systems, it is required to accurately calculate the resolution and the aperture angle of the beam.